Microtome cooling and dehumidifying



Feb. 22, 1966 L. A. DE PAS MICRO'IOME COOLING AND DEHUMIDIFYING Filed May 6, 1963 3 Sheets-Sheet 1 Feb. 22, 1966 L. A. DE PAS MICROTOME COOLING AND DEHUMIDIFYING 3 Sheets-Sheet 2 Filed May 6, 1963 Feb. 22, L. A. DE PAS MICROTOME COOLING AND DEHUMIDIFYING Filed May 6, 1963 3 Sheets-Sheet 5 COMPRESSBR United States Patent O 3 236 133 MICROTOME COOLIlQG AND DEHUMIDIFYING Laddie A. De Pas, Sotlus, Mich, assignor to Whirlpool Corporation, a corporation of Delaware Filed May 6, 1963, Ser. No. 278,014

19 Claims. (Cl. 83-170) This invention relates to an air cooling apparatus for a microtome.

Microtomes are used to cut very thin sections from specimens, particularly biological specimens, so that they can be examined microscopically. The usual microtome employs a knife in combination with an apparatus that holds the specimen and moves it in relationship to the knife to slice off the thin sections. Such cut sections ordinarily vary in thickness between a fraction of a micron and a few microns.

When the specimens are biological, such as secured during an operation on the body, they are customarily frozen as rapidly as possible so that they can be handled. They are maintained frozen and transported to the microtome for slicing in thin sections.

One of the features of this invention is to provide an improved cooling apparatus for a microtome which provides a circulating cold dry atmosphere that contacts the specimen holder and thus the specimen thereon and the cutting means during the operation of the microtome so as to maintain the specimen and the sections cut therefrom in frozen condition.

Another feature of the invention is to provide such an apparatus wherein the cold dry air is circulated in a closed path continuously during which the air is continuously cooled and dehumidified.

Another feature of the invention is to provide such an apparatus having improved means for removing excess moisture from the cooling heat sink in order that this heat sink will operate with a high degree of efiiciency continuously in removing the moisture in cooling the specimen.

A further feature of the invention is to provide such an apparatus including improved means for maintaining specimens in frozen condition preparatory to mounting on the microtome for cutting in which the cold heat sink is used to keep the specimens chilled.

Other features and advantages of the invention will be apparent from the following description of certain embodiments thereof taken in conjunction with the accompanying drawings. Of the drawings:

FIGURE 1 is a longitudinal sectional view of an apparatus embodying the invention taken substantially along line 11 of FIGURE 2.

FIGURE 2 is a plan view of the apparatus of FIGURE 1 partially broken away.

FIGURE 3 is a fragmentary sectional view taken substantially along line 33 of FIGURE 2.

FIGURE 4 is a wiring diagram of the electrical system of the embodiment.

FIGURE 5 is a fragmentary perspecive view of a second embodiment of the invention.

In the embodiment of FIGURES 1-4 inclusive there is disclosed a conventional microtome mounted on a supporting table 11 forming a part of the apparatus 12 embodying the invention. This microtome includes a front transverse knife 13 mounted on a ledge 14 beneath the holder 15 for the specimen 15a. On one side of the microtome there is provided a rotatable walled disk 16 that is rotated by means of a handle 17. The disk 16 and handle 17 are exposed through an opening 18 in an enclosing cover 19 that is movably mounted about a hinge 20 on the table 11. As shown in FIGURES 1 and 2, the cover 19 encloses the microtome 10 but can be rotated away from the microtome about the hinge 20. The front wall 21 of the cover 19 contains a hinged double paneled window 22 with an insulating air space therein through which a specimen on the holder 15 may be viewed during the cutting operation. Specimen holders are inserted and sliced sections removed through the opening covered by this window.

The air cooling apparatus is self-contained and is easily moved on a supporting surface such as a floor 23 by means of a front handle 24. As shown in FIGURE 1, the apparatus is mounted on supporting casters 25.

In order to cool and dry a circulating air stream in the apparatus there is provided refrigerating apparatus in a bottom machine compartment 26. This refrigerating apparatus includes the customary compressor 27, condenser 28, refrigerant receiver 29 and blower 30, all located in the compartment 26. Cooling air is admitted to the compartment 26 through grill 32 in one wall of the machine compartment and is emitted through louvers 3 1 in an opposite wall. In the embodiment shown, the grill 32 is positioned adjacent the condenser 28 and the blower 30 is located behind the condenser so as to pull cooling air therethrou'gh.

In order to cool and dehumidify the air stream there is provided an insulated liquid heat sink 33 in the form of a solution, such as an aqueous solution of a salt, and particularly a hygroscopic salt such as calcium chloride. This heat sink 33 is enclosed in an insulated housing 34 that is shown positioned above the machine compartment 26. The liquid solution 33 forming the heat sink does not fill the enclosing housing 34 so that the heat sink solution has its upper surface 35 exposed.

In order to chill the liquid solution heat sink 33 to a subfreezing temperature the evaporator 36 of the refrigeration system is immersed in the liquid 33. The compressor 27, receiver 29, condenser 28 and evaporator 36 are connected by the usual refrigerant tubing 37 in a refrigerant circuit which of course also includes the customary capillary 38. Operation of the refrigeration system to maintain a desired low temperature in the liquid solution 33 is controlled by a customary thermostat 39 controlled by a sensing bulb 40 immersed in the liquid solution 33.

In order to chill the specimen holder 15 and thus a specimen held therein as well as the knife 13, there is provided a cooling air conduit 41. This conduit which has insulated side walls throughout its extent includes one portion 42 in the hinged cover 19, a second portion 43 communicating at its bottom with the top of the liquid heat sink housing 34 and at its top with the rear end of the conduit portion 43 and a cooling chamber portion 44 at the front of the apparatus and vertically above the front part of the liquid heat sink 33.

As shown in FIGURES 1 and 2 the front end of the first air conduit portion 42 empties directly downwardly on the specimen holder 15 so as to contact first a specimen held thereon. From here the air separates into two streams on opposite sides of the holder 15 and contacts the knife 13 after which these streams flow through two laterally spaced openings 45 into the top of the cooling chamber 44.

Toward the bottom of the cooling chamber 44 there is located a transverse partition 46 extending entirely across the chamber and provided with a large central opening 47 surrounded by an upwardly extending flange 48. The partition 46 provides a blower space 49 and air flow from the cooling chamber 44 is through a pair of spaced openings 50 into the top of the heat sink housing 34 above the liquid surface 35.

Extending vertically through the cooling chamber 44, partition opening 47 and into the liquid 33 is a hollow tube 51 rotatably mounted in a top bearing 52 in the top wall of the cooling chamber 44 and a bottom bearing 53 in the top wall of the chamber 34 that contains the air opening 50. This tube 51 is rotated through a belt drive 54 by means of an electric motor 55.

Mounted on the upper end of the tube 51 within the cooling chamber 44 are a plurality of upwardly dished or concave disks 56. The tube 51 has a plurality of small openings 57 adjacent the top of each disk 56 for providing liquid flow from the interior of the hollow tube onto the top surface of the disk.

Also mounted on the hollow tube 51 immediately beneath the partition 46 is a blower wheel 58. The blower 58 and opening 47 are so arranged that air flowing through the opening goes to the center of the wheel so that the blower operates in the customary manner.

The bottom of the tube 51 that is immersed in the liquid 53 is provided with a customary pumping opening 59 so that on rotation of the tube 51 liquid 33 is lifted within the tube and fed through the openings 57 onto the top surfaces of the disk 56 where it is sprayed in the form of small droplets throughout the cooling chamber 44. This sprayed liquid falls onto the top of the partition 46 and is prevented from entering the blower 58 by the flange 48. The liquid can, however, flow to the bottom of the blower space 49 by means of a recessed side wall channel 60 in the side wall 61 forming the cooling chamber 44.

From the bottom of the blower space 49 the liquid is returned to the liquid heat sink 33 by way of a J-shaped drain tube 62 having its exit end 63 immersed in the liquid 33.

During operation of the apparatus of this invention the rotation of the tube 51 and thus the blower 58 causes air to flow in a closed circuit through the conduit 41. As shown, the air flows downwardly through the cooling chamber 44 where it contacts small droplets, illustrated at 64, of heat sink liquid 33. This contact serves to chill and dehumidify the air as previously described. The sprayed liquid is returned to the heat sink 33 by Way of the channel 60 and tube 62 also as previously described.

The chilled and dehumidified air from the cooling chamber 44 is then drawn by the blower 58 through the opening 47 and forced through the openings 50 into the top of the liquid heat sink housing 34. In here the air flows across the top surface 35 of the liquid 33 where it is further chilled and dehumidified and from the rear of the heat sink housing 34 flows upwardly through the conduit portion 43 into the conduit portion 42 in the cover 19. In this portion 42 the chilled dry air is forced forwardly toward the front of the apparatus and then downwardly through an opening 65 directly onto the specimen holder 15 so as to immediately contact a specimen therein before contacting the knife 13. From here the air flows through the pair of openings 45 into the top of the cooling chamber 44 to start a new circulation as previously described.

Because of the mounting of the cover 19 about the hinge 20 it is very easy to rotate the cover 19 about the hinge 28 to expose the specimen holder 15 and knife 13 when servicing of the microtome is required. Front wall 21 contains a transparent window 22 which is hinged and allows access to the specimen and specimen holder before and after the slicing operation.

During the continuous operation of this apparatus it of course extracts moisture from the specimen and also removes any moisture admitted 'by the opening and closing of the cover 19. This extracted moisture is of course dissolved in the liquid heat sink solution 33 and tends slowly to increase the volume of the liquid. This increase in volume causes a float 66 to rise. Loosely suspended from this float 66 is a valve 67 having an enlarged head 68 on the interior of the drain tube 62 so that when the float 66 rises a predetermined distance the valve head closes an opening 69 in the exit end 63 of the tube 62. Because of this enlarged head 68 internal liquid pressure Within the tube 62 holds the valve closed even as this internal pressure diminishes.

With the exit opening 69 closed liquid flowing in the tube 62 is diverted by way of a side tube 70 into the bottom of a liquid evaporator 71. Positioned in this evaporator is a float 72 which rises with the increasing liquid level in the evaporator to close a switch 73 which energizes an electric heater 74 in the bottom of the evaporator or boiler 71. This heater thereupon boils off excess water which passes out in the form of water vapor through rear openings 75.

As the water is boiled ofl in the boiler 71 the internal pressure within the tube 62 decreases. However, because of the enlarged head construction 68 of the valve 67 the valve does not immediately open until the level of the solution 35 drops. When the solution level has dropped to a predetermined level, float 72 forces valve 67 to open. This allows all the liquid flowing into tube 62 to return to liquid heat sink 33 through opening 69.

FIGURE 3 illustrates a device for storing specimens in frozen condition preparatory to cutting sections with the apparatus of this invention. Here there is provided on the table 11 an insulated liquid reservoir 76 of an anti-freeze liquid, such as ethylene glycol, and this reservoir is connected in a closed circuit including an outlet conduit 77, an inlet conduit 78 and a coil 79 therebetween immersed in the'liquid 33. With this arrangement liquid in the reservoir 76 is continually circulated down the conduit 77, through the coil 79 and back up the conduit 78 so as to be chilled by the liquid heat sink 33.

This movement of liquid is provided by a pump which operates on the magnetic stir principle. On the bottom of the insulated housing 80 containing the reservoir 76 there is rovided an electric motor 81 which when energized rotates a magnet 82. Directly opposite this magnet 82 and located in the bottom of the reservoir 76 is a second magnet 83 that is free to move within the bottom of the reservoir. This magnet 83 is enclosed in a housing 84 at the bottom of the reservoir with the housing including a dividing wall 85 between the reservoir ends of the conduit 7'778. Extending from the housing 84 and sur rounding the magnet 83 is a cylindrical flange 86. Located in the housing 84 immediately above the second magnet 83 is an opening 87.

The top of the reservoir housing 80 on the top of the table 11 is enclosed by an insulated cover 88 the top of which is provided with resilient material such as sponge rubber 89. Within the cover 88 and beneath the resilient material 89 there are located three inverted metal cupshaped members 90 that serve as auxiliary heat sinks operating in conjunction with the heat sink reservoir 76. These cups are adapted to enclose metal heat transfer members 91 each made up of a stem 92 extending down into the reservoir 76 and a top disk 93 integral with the stem adapted to support a specimen thereon. A specimen freezing system in which similar heat transfer members are used is disclosed and claimed in the copending application of Everett F. Cox, Serial No. 278,828, filed May 8, 1963, now Patent No. 3,176,472, and assigned to the same assignee as the present application.

With the above described construction rotation of the first magnet 82 by the motor 81 causes corresponding rotation of the second magnet 83 in the bottom of the reservoir 7 6. This rotation of the magnet 83 causes liquid to be forced outwardly around the bottom edge of the flange 86 while simultaneously drawing in liquid from the main reservoir through the opening 87. The outwardly forced liquid is thereby forced down the conduit 77, through the coils 79 and back up the conduit 78 to the reservoir 76 to complete the circuit. As can be seen, the liquid in the reservoir 76 is continually circulated to extract heat from the specimens by way of the members 91 and transfer this heat to heat sink 33.

FIGURE 4 shows a conventional wiring diagram for the apparatus. The blower motor 94 is connected across the electric lines 95 and is controlled by a master line switch 96 and a three position switch 97 in series. Connected in parallel across the lines 95 are the compressor motor 98 and the heater 74 for the boiler 71. The compressor 98 is in series with the thermostat switch 39 which is operated as previously described by the bulb 40 through a bellows 99. The heater 74- is in series with its float operated switch 73 to function in the manner previously described.

FIGURE 5 illustrates another embodiment of the invention. Here the microtome 100 is exposed and the holder 101 and knife 102 may be enclosed by a hinged cover 103 having a hinged window 104 therein that is similar to the previous window 22. This cover 103 is movable about a hinge 105 and is shown in FIG. 5 in open position. Chilled, dehumidified air is directed onto the specimen held in the holder 101 through one opening 106 and this air is returned to the cooling and dehumidifying portion of the apparatus through an opposite opening 107.

In a typical embodiment of this invention the solution 33 was a saturated solution of calcium chloride. The solution temperature was maintained at about 18 F. and the air temperature fed through the upper opening 65 was about l2 F. while the return air temperature into the cooling chamber 44 was about +40 F. The microtome knife was maintained during operation of the apparatus at about 8 F. and the system extracted about 2500 3000 B.t.u. per hour.

As can be seen, the apparatus of this invention has a number of new and unobvious advantages. Thus, it is completely self-contained and can be moved about from place to place. It operates continuously to provide dry cold air and because liquids are not directed against the specimen or the knife there is no build-up of frozen liquid such as frost on the specimen or the knife. The operation of the apparatus is automatic with the heat sink temperature being maintained at the proper level automatically and with extracted and dissolved moisture being removed periodically and automatically. As the air is dry when it contacts the specimen and knife there is no frost deposited from the air. No defrosting of the cooling evaporator 36 is required, as this evaporator is immersed in the liquid heat sink 33.

Having described my invention as related to the embodiments shown in the accompanying drawings, it is my intention that the invention be not limited by any of the details of description, unless otherwise specified, but rather be construed broadly within its spirit and scope as set out in the accompanying claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Air cooling apparatus for a microtome having a specimen holder and cutting means for the specimen, comprising: means defining a closed system cooled air conduit in which said holder and cutting means are located; and means for guiding substantially all the air in said conduit in a stream directly against the specimen in said holder prior to said air reaching said cutting means.

2. Air cooling apparatus for a microtome having a specimen holder and cutting means for the specimen, comprising: means defining a closed system cooled air conduit in which said holder and cutting means are located; and transparent viewing means in said conduit for viewing said specimen during cutting.

3. The apparatus of claim 2 wherein said conduit and viewing means are each thermally insulated.

4. Air cooling apparatus for a microtome having a specimen holder and cutting means for the specimen, comprising: means defining a closed system cooled air conduit in which said holder and cutting means are located; means for moving air through said conduit; means providing in said closed system a liquid heat sink chilled to a subfreezing sink temperature; and means for contacting the moving air with said liquid to dry and chill the air.

5. Air cooling apparatus for a microtome having a specimen holder and cutting means for the specimen, comprising: means defining a closed system cooled air conduit in which said holder and the cutting means are located; means for moving air through said conduit; means providing a cooling chamber as a part of said closed system air conduit; means providing in said closed system a liquid heat sink chilled to a subfreezing temperature; means for distributing a portion of liquid from said heat sink in thermal contact with moving air in said cooling chamber to dry and chill the air therein; and means providing an auxiliary cooling chamber as a part of said closed system conduit, said auxiliary cooling chamber including an exposed surface of said heat sink for direct contact of said moving air with said surface.

6. Air cooling apparatus for a microtome having a specimen holder and cutting means for the specimen, comprising: means defining a closed system cooled air conduit having one portion in which said holder and cutting means are located; and means mounting said one portion for movement relative to said holder and cutting means for providing access to said holder and cutting means on movement of said one portion.

7. Air cooling apparatus for a microtome having a specimen holder and cutting means for the specimen, comprising: means defining a closed system cooled air conduit having one portion in which said holder and cutting means are located; means mounting said one portion for movement relative to said holder and cutting means for providing access to said holder and cutting means on movement of said one portion; and transparent viewing means in said one portion for viewing said specimen during cutting.

8. Air cooling apparatus for a microtome having a specimen holder and cutting means for the specimen, comprising: means defining a closed system cooled air conduit in which said holder and cutting means are located; means for moving air through said conduit; means providing a cooling chamber as a part of said closed system air conduit; means providing in said closed system a chilled liquid heat sink; and movable means located in both said cooling chamber and said liquid heat sink means for simultaneously transferring portions of liquid from said heat sink to said cooling chamber, distributing said portions in thermal contact with moving air in said cooling chamber and operating said air moving means.

9. Air cooling apparatus for a microtome having a specimen holder and cutting means for the specimen, comprising: means defining a closed system cooled air conduit in which said holder and cutting means are located; means providing :a cooling chamber as a part of said closed system air conduit; means providing in said closed system a chilled liquid heat sink; means for distributing portions of liquid from said heat sink in thermal contact with moving air in said cooling chamber; catch means for receiving said distributed portions; air moving means adjacent said catch means for moving air through said closed system conduit including said cooling chamber; and means for conveying liquid from said catch means to said liquid heat sink in a path that is externally of said air moving means.

10. Air cooling apparatus for a microtome having a specimen holder and cutting means for the specimen, comprising: means defining a closed system cooled air conduit in which said holder and cutting means are located; means for moving air through said closed conduit; means providing in said closed system a cooling chamber as a part of said air conduit; means providing in said closed system a chilled liquid heat sink; means for spraying portions of liquid from said heat sink in thermal contact with moving air in said cooling chamber; catch means in said cooling chamber for catching falling liquid from said spraying; means forming one path in said closed system for moving air relative to said catch means; and means forming a second separate path for liquid from said catch means.

11. The apparatus of claim 10 wherein said catch means comprises a transverse partition beneath which is located said air moving means and having an air opening therein protected from substantial liquid flow therethrough by bafiie means adjacent said opening.

12. Air cooling apparatus for a microtome having a specimen holder and cutting means for the specimen, comprising: means defining a closed system cooled air conduit in which said holder and cutting means are located; means providing a cooling chamber as a part of said closed system air conduit; means providing in said closed system a chilled liquid heat sink; catch means comprising a transverse partition in said cooling chamber having an air opening therein protected from substantial liquid flow through said opening bybaffle means; a rotatable member extending through said opening; means mounted on said rotatable member in said cooling chamher for spraying liquid therein; means mounted on said rotatable member beneath said partition for moving air in said closed system conduit; and means for conveying liquid from said catch means to said liquid heat sink in a path that is externally of said air moving means.

13. The apparatus of claim 12 wherein said cooling chamber is located above said liquid sink and said rotatable member extends downwardly into said sink and carries pump means for lifting liquid from said sink to said spraying means.

14. Air cooling apparatus for a micr-otome having a specimen holder and cutting means for the specimen, comprising: means defining a closed system cooled air conduit in which said holder and cutting means are located; means providing a cooling chamber as a part of said closed system air conduit; meansproviding in said closed system a chilled liquid heat sink beneath said cooling chamber; catch means comprising a transverse partition in said cooling chamber having an air opening therein protected from substantial liquid fiow through said opening by bafiie means; a rotatable member extending through said opening into said liquid heat sink, said rotatable member having a hollow interior and provided on its lower end with pump means for lifting liquid up said interior; spaced means mounted on said rotatable member in said cooling chamber for spraying liquid therein, said rotatable member being provided with flow means communicating with said spaced means to deliver liquid thereto; blower means mounted on said rotatable member beneath said partition for moving air in said conduit; and means for conveying liquid from said catch means to said liquid heat sink in a path that is externally of said air moving means.

15. Air cooling apparatus for a microtome having a specimen holder and cutting means for the specimen, comprising: means defining a closed system cooled air conduit in which said holder and cutting means are located; means for moving air through said conduit; means providing a chilled liquid heat sink; means for contacting the moving air in said closed system conduit with said liquid to dry and chill the air, the liquid tending to increase in volume from dissolved moisture from said air; a liquid evaporator separate from said liquid heat sink having evaporating means; means for directing excess liquid after a predetermined increase in volume to said evaporator; and means operable by liquid in said evaporator to activate said heating means to evaporate liquid.

16. Air cooling apparatus for a microtome having a specimen holder and cutting means for the specimen, comprising: means defining a closed system cooled air conduit in which said holder and cutting means are located; means providing a cooling chamber as a part of said closed system air conduit; means providing in said closed system a chilled liquid heat sink; means for distributing portions of liquid from said heat sink in thermal contact with moving air in said cooling chamber; a conduit having an exit for returning said liquid portions to said liquid heat sink, the liquid tending to increase in volume from dissolved moisture from said air; a liquid evaporator separate from said liquid heat sink having evaporating means; means for directing excess liquid after a predetermined increase in volume to said evaporator from said conduit, said directing means including a valve for closing said conduit exit after said predetermined volume; and means operable by liquid in said evaporator to activate said heating means to evaporate liquid, said valve having means associated therewith for maintaining the valve closed until a predetermined volume of liquid has been evaporated.

17. In an air cooling apparatus for a microtome having a specimen holder, cutting means for the specimen, and a cold liquid heat sink for cooling the specimen, a device for maintaining specimens prior to mounting on said holder, comprising: a liquid reservoir; means for transferring liquid to and from said reservoir in heat transfer relationship with said heat sink; and insulated means for mounting a specimen in heat transfer relationship with said reservoir.

18. The device of claim 17 wherein the liquid transferring means comprises a closed circuit conduit including a coil immersed in said heat sing and a magnetically operated pump means in said reservoir.

19. The device of claim 17 wherein said specimen mounting means includes a heat transfer member having one portion extending into the liquid in said reservoir and a second portion out of said liquid for supporting said specimen.

References Cited by the Examiner UNITED STATES PATENTS 2,292,973 8/ 1942 Richards.

2,379,932 7/1945 Schoepflin 83l70 2,507,632 5/1950 Hickman 62435 2,670,657 6/1954 Smith 83-170 2,843,014 7/1958 Sitte 83170 2,859,946 11/ 1958 Boyle 623 14 2,961,908 11/1960 Moran 83170 3,027,734 4/1962 Mills 62-435 WILLIAM W. DYER, 111., Primary Examiner.

ANDREW R. JUHASZ, Examiner. 

1. AIR COOLING APPARATUS FOR A MICROTOME HAVING A SPECIMEN HOLDER AND CUTTING MEANS FOR THE SPECIMEN, COMPRISING: MEANS DEFINING A CLOSED SYSTEM COOLED AIR CONDUIT IN WHICH SAID HOLDER AND CUTTING MEANS ARE LOCATED; AND 